All matter is made of atoms The idea of the atom first came from Greek philosopher Democritus 400 B.C Greek word “atomos” means not to be cut Did not use scientific method No experiments to support idea

In late 1808 he looked at all the data from experiments- his and others Developed his own theory Theory was accepted because of all the evidence

Dalton’s Atomic theory 1. Dalton said all matter was made up of atoms- tiny particles of that can’t be broken up 2. Dalton said atoms of the same element are identical 3. Dalton said atoms of different elements join to form molecules.

Parts of Atoms An atom is mostly empty Protons and neutrons are located in the nucleus Electrons are located outside the nucleus

Atoms can be broken. Proton – positively charged (+), big mass, found in nucleus Electron – negatively charged (-), very small mass, in orbitals Neutron – no charge (0), about the same mass as a proton, in nucleus

Atom’s Subatomic Particles Proton Positive Charge Found in the nucleus Neutron Neutral charge Found in the nucleus Electron Negative charge Possibly found in orbitals outside the nucleus

The nucleus of an atom contains protons and neutrons. Protons have positive charges and neutrons are neutral… Therefore the nucleus of an atom must have a ________________________ Charge.

Electrons move around the nucleus like planets move around the sun. He was partially right. Each electron has it’s own energy level Oct. 7, 1885 to Nov. 18, 1962

Energy Level Energy levels describe the path the electron takes around the nucleus Energy levels farther from nucleus have more energy Gain energy they move away from the nucleus Energy levels lose energy as they move toward the nucleus Only certain energies are allowed in each atom

There is only a probability of finding an electron in an orbital It is impossible to know the exact location and the speed and direction of an electron

The Periodic Table Elements are Listed in order of increasing number of protons (atomic number) Periodic Law- when the elements are arranged in order of increasing number of protons, the properties tend to repeat in a pattern

Dmitri Mendeleev organized the elements by increasing atomic mass. He was partially wrong…it should be by increasing Atomic number.

Counting the pieces Atomic Number- the number of protons that are in a nucleus of an atom Determines the type of atom and element Mass number- number of protons and neutrons in the nucleus of an atom To get the number of neutrons you subtract the atomic mass and the atomic number. Electrons are the same number as protons if neutral.

7 protons 7 electrons 14-7 = 7 neutrons

79 protons 79 electrons = 118 neutrons

Isotopes Isotopes are atoms of the same type that have different numbers of neutrons They behave identically They just have different masses Mass number is written after the name Hydrogen – 1 Hydrogen – 2

The Periodic Table Atoms in the same column have similar properties Columns are called groups or families They have similar properties because they have the same number of valence electrons Rows are called periods

Metals Hard and shiny (luster) 3 or less valence electrons Form cations (+) by losing electrons (e-) Good conductors of heat and electricity Nonmetals Gases or dull, brittle solids 5 or more valence electrons Form anions (-) by gaining electrons (e-) Poor conductors of heat and electricity Metalloids (semi-metal) Appearance will vary 3 to 7 valence electrons Form cations (+) and anions (-) Conduct better than nonmetals but not as well as metals

Valence electrons are electrons found in the outermost shell of an atom. Valence electrons are electrons found in the outermost shell of an atom. The octet rule says that atoms tend to gain, lose or share electrons so as to have _______________ electrons in their outer electron shell. This does not apply in all bonding situations, but will be sufficient for what we will cover.

Valence electrons The electrons in the outermost energy level Responsible for most of the chemical properties When two atoms interact (bond), the outside electrons are the ones affected

Groups Alkali Metals Alkaline-Earth Metals Transitional Metals Halogens Noble Gases

Properties of Metals Luster – shiny. Ductile – drawn into wires. Malleable – hammered into sheets. Conductors of heat and electricity.

Alkali Metals Very reactive with other elements Not found alone in nature Have one valence electron Easily lose electrons to form a 1+ ion (cation)

Alkaline Earth Metals Less reactive Have two valence electrons Lose their 2 valence electrons to form a 2+ ion (cation)

Transition Metals Less reactive Often found alone in nature Form many different ions

Halogens Very reactive Have 7 valence electrons Gain one electron to form a 1- ion (anion)

Noble Gases Do not react Will not form compounds Considered inert because they do not react with other elements. They have a full outer shell of 8 valence electrons. They will stand alone in nature

Ions Ions are atoms with a charge Different number of protons and electrons Form by changing the number of electrons Ionization- adding or removing electrons from an atom or group of atoms Two types 1. anion 2. cation

Cations Ions with a positive charge More protons than electrons Formed by losing electrons Happens to atoms with few valence electrons Atoms Lose electrons to get down to full outside energy level Written as a superscript Na + Ca 2+

Anions Anions are Negative ions More electrons than protons Form by gaining electrons Happens to atoms with many valence electrons Fill up outer energy level Written as a superscript F - O 2-